A scanner has become a part of modern day computing and most homes and office IT ranges will include one of these wonderful devices. It is intended to optically scan a number of objects such as handwriting, printed text, photos and will then convert them into a digital image. The most common type will be the desktop or flatbed scanner which allows you to place your document on a glass window, which in turn will scan and digitally copy the item. There are numerous other scanning devices such as hand held models or wands, and many commercial and industrial sites take advantage of 3D scanners.
One of the most important factors to consider when scanning documents is the resolution of the device. The resolution is actually measured in dots per inch (DPI). Typically the higher the resolution of the scanner, the clearer you can expect the image to be. On average many scanners use a resolution of 1200 DPI which is fine for most everyday tasks however film or enlargements will usually require a much higher resolution to maintain a decent quality image. It must be said though that higher resolution does not automatically mean that you will receive a higher quality scan.
In order to scan a typical digital photo you may produce, on average, a file of around 1MB in size however scanning at a high resolution for enlargements can use as much as 60MB – 70MB. A scanner will usually aim to read the colors blue, green and red from the data presented. This data is then read and processed and sent to the computer via the scanner’s output interface. The dots per inch are also referred to a pixels per inch (PPI) or samples per inch (SPI). You can expect a flatbed scanner to scan up to 5,400 PPI whereas a drum scanner will produce an optical resolution of up to 12,000 PPI.
A drum scanner will scan image information first and foremost. Your originals should be mounted onto an acrylic cylinder, or the scanner drum and this will rotate at a fairly high speed and will then pass the object in front of the optics. A drum scanner is most commonly used to scan original artworks and allows you to copy originals of up to 11 inches by 17 inches in size.
A flatbed scanner is the most typically found in people’s homes. It will be composed of a glass pane underneath which you will find a xenon or cold cathode fluorescent bright light. You should place your document down on the glass pane and then close the opaque cover to ensure that no natural (or unnatural) light filters through. The image will become visible to the detector because of the light that it reflects. You will find that a transparent image will not scan in the same way and will require additional accessories however most modern day scanners have this option already built in.
You also have the option of hand scanners that will either come as a digital or 3D scanner. These can best be described as a manual device that you should run over the surface of the image that you wish to scan. You will need a very steady hand and if you do shake or if you are unable to hold the scanner steady your images may well come out distorted. Most hand scanners also have a window through which you can view the image you are about to scan.
Many manufacturers claim that they have scanners that can scan items with a resolution as high as 19,200 PPI however in most instances this will provide little, or no, additional value. You must also remember that the higher the resolution, the bigger the file will be. On average if you double the resolution you can expect the file to end up 4 times as big. Another aspect of many High Resolution Scanners is their ability to improve the density range. If the scanner has an equally high density range, this will allow you to reproduce certain details such as shadows or an increased brightness.
Many High Resolution Scanners have some great additional features. These include image editing software which will automatically remove specks of dust or scratches. You can also adjust the image to improve the color balance should you wish. You may also have access to optical character recognition (OCR) which allows you to scan words into a text document that can be edited in a word processor at a later date. Should you have any old written items that you wish to convert to digital, this function is ideal. Many scanners also allow for one touch scanning which helps you to immediately convert text into a digital PDF file.